This disclosure generally relates to systems, methods for alerting pilots during landing when current airplane braking is not sufficient to avoid runway excursions.
There are existing methods and devices for alerting pilots of the risk of a runway excursion (i.e., the airplane going off the end of the runway) during landing. However, the existing methods and devices rely on pilot perception and interpretation of the alerts as well as various landing information and data, such as the airplane's current deceleration rate, runway conditions or remaining runway distance, to determine an appropriate corrective action, and then the pilot must take the corrective action in a timely manner.
For example, most runways include runway landmarks such as billboards that identify the distance remaining until the end of the runway. Such landmarks are used by pilots to estimate whether the airplane's performance on the ground (for example, its braking performance) is in-line with the planned performance and whether there remains a sufficient length of runway for the airplane to reduce its speed to enable the airplane to turn into an exit taxiway or stop. Runway landmarks also require that pilots be able to read the billboards in all conditions and then use that information to evaluate how the remaining distance relates to the airplane's braking performance. That determination must take into account the airplane's available deceleration tools, including autobrake settings (e.g., automated wheel-based braking), reversing the engine thrust (e.g., thrust reversers), and aerodynamic braking using wing flaps (e.g., spoilers or speedbrakes).
Other automated aircraft systems are available that provide visual and/or audible call-outs of various airplane performance characteristics for pilots, including remaining runway distance and runway conditions. Such systems are referred to in the aircraft industry generically as proximity warning systems or terrain awareness and warning systems (TAWS), and generally aim to prevent terrain accidents during controlled landings. A TAWS may comprise: (1) a computer system (as defined in the penultimate paragraph of the Detailed Description hereinafter) that executes operations in accordance with an algorithm that uses aircraft inputs such as position, attitude and air speed, along with databases of terrain, obstacles and airport information (including runway information) to predict a potential conflict between the aircraft's flight path and an obstacle, and (2) alert devices for providing visual and aural alerts to pilots when flight into an obstacle is predicted by the computer system. The TAWS may include a software module, which uses GPS position data and databases to provide aural callouts and advisories that supplement flight crew awareness of the airplane's position during taxiing, takeoff, final approach, landing and rollout, including to help reduce the risk of a runway excursion by providing timely callouts as the aircraft approaches the end of the runway. For example, the TAWS runway module provides Distance Remaining callouts to inform pilots of remaining runway distance for information purposes. Whether a callout should be issued or not is determined by comparing the current aircraft position along the runway to the location of the end of the runway. The pilot interprets the information provided and then determines what corrective action to take.
Pilots estimate their performance on the ground using runway landmarks (like distance remaining billboards) with reference to what was planned. This would require that the pilots can read the billboards in all conditions (if there are billboards on the runway) and then assess how that relates to their braking performance. A TAWS runway module provides distance remaining callouts, but the pilot still needs to relate this with braking performance. A problem can arise when a pilot uses insufficient braking for current runway conditions and/or remaining runway distance.